Fuel tank cap



FIG. 1 is a perspective view of a fuel tank cap showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The broken lines in the drawings illustrate portions of the fuel tank cap that form no part of the claimed design. 

CLAIM The ornamental design for a fuel tank cap, as shown and described. 